COMP140 Individual Creative Computing Project

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Learning Outcomes

After this session you will be able to:

• Select the appropriate method for communication
• Outline the difference between I2C and SPI
• Implement a hardware interface between the Arduino and a sensor

What is Serial Communication?

• Arduino to Multimedia Computer (retro term alert)
• Arduino to Arduino
• Arduino to sensors

Some kind of picture?

Types of Serial Communications

• I2C
• RS232
• USB
• R2422
• CAN
• Microwire
• RS485
• SPI
• TTL

Protocols

A protocol is the language that governs communication between systems or devices.

• Midi
• DMX-512
• X10
• USB
• RS485
• UDP/IP
• TCP/IP

% ## Physical Agreement

% ## Timing Agreement % Interfaces require

% ## Electrical Agreement

% ## Package Size

% ## Serial vs. Parallel

## Universal asynchronious Receiver/transmitter (UART)

Serial/UART

• This is how an Arduino talks to a computer
• Arduino has an onboard UART to Seral Converter
• Requires an agreed baud rate: Serial.begin(9600)
• Two communication lines - RX to receive and TX to transmit
• TX connects RX, RX to TX
• Used by some peripherals such as Bluetooth modules

When Time Goes Wrong

Inter-Intergrated Circuit (I<sup>2</sup>C)

• Pronounced I Square C
• Uses a clock Signal
• Two communication lines - SDA (data) and SCL (clock)
• Multiple I<sup>2</sup>C devices can communication on the same data lines (bussed)
• Slave devices have an address

I<sup>2</sup>C Bus Example

Wire Library

• I<sup>2</sup>C Library for Arduino
• Arduino can be either host of slave
• Particularly useful for wired Arduino-to-Arduino communication

I<sup>2</sup>C Communication Example

Serial Peripheral Interface (SPI)

• Uses a clock signal
• Requires 4 lines
• MISO - master in slave out
• MOSI - master out slave in
• SCK - serial clock
• CS - chip select
• Not addressed - each slave device requires a discrete chip select line.

SPI Bus Example

SPI Communication Example

Logic Analysers

• Not doing what you expect? Spy on them!
• Logic analysers are the digital equivelant of an oscilloscope
• Can have up to 8 signal capture lines
• Capture digital logic (HIGH or LOW)
• Easy to connect to existing circuits
• USB connection for data capture
• We have a couple in the Games Academy

Logic Analyser Software

Differential Signal

• Low voltage signals are susceptible to noise over long distance
• Noise can turn a digital 1 into a 0
• Differential Signal is one solution
• Used by USB and in professional audio
• The hardwork is done for you: PCA9615 chip converts I<sup>2</sup>C to diff

How does Differential Signal Work?

• Two lines carry the same signal, but one is inverted
• The two lines cancel each other out
• All that is left is the noice
• The noise is then cancelled out

Activity - MPU-6050